Four people were shot Monday morning on a Blue Line train in west suburban Forest Park.

At about 5:30 a.m., officers responded to the Forest Park Blue Line station at 711 Desplaines Ave. and found four people shot on the train, Forest Park police said.

Three people died at the scene, police said, and a fourth was transported to Loyola University Medical Center in Maywood, where he later died.

“It’s a horrible situation, you definitely don’t want to wake up in it,” Forest Park Police Deputy Chief Christopher Chin told reporters outside the station. “Everybody should be enjoying their time off… it’s horrible.”

The shooting occurred while the train was in motion and all the fatalities were passengers, Chin said.

Police radio reports Monday morning said it was unclear whether anyone witnessed the shooting.

“We have multiple shell casings… several passengers apparently deceased,” someone could be heard saying over the radio. “… It looks like three people are unresponsive to the same carriage. … It looks like there are no witnesses. No one reported this.”

Forest Park Mayor Rory Hoskins called the shooting “an exception” and asked Springfield leaders to consider investing in additional public safety resources as part of a CTA mass transit revamp to “support a small community like Forest Park.”

Hoskins told WGN-TV the victims were shot at close range as they slept on the train.

“Forest Park is the only community in Cook County … with two major railroads that terminate in Forest Park,” Hoskins told reporters. “It’s a terrible tragedy that four people died over the Labor Day weekend.”

Forest Park police worked with CTA security to develop a description of the suspected shooter, and Chicago police arrested a person matching that description on the Pink Line train. A firearm was also recovered.

“We extend our condolences to those who lost loved ones in this senseless act of crime – our thoughts and prayers are with them,” CTA President Dorval R. Carter Jr. said in a statement.

“While this was an isolated incident, this abhorrent and egregious act of violence should never have occurred, much less on a public transit train,” the CTA said in a statement. “As soon as this matter was reported, the CTA immediately dispatched resources to assist the Forest Park Police Department in their investigation, including reviewing all available security footage, which proved critical in assisting local law enforcement.”

The age and gender of the victims were not initially revealed.

Officers believe the suspect in custody was the only shooter and the shooting was an “isolated incident.”

“This could happen anywhere, of course there is a little more concern because it happened on a mass transit system, but it is important to remember that there are safety measures in place,” Chin said.

Blue Line trains between Forest Park and Austin resumed service Monday evening at approximately 7:30 p.m.

The entrance to the Forest Park Blue Line station was blocked with police tape as police investigated the scene. As of 11:45 a.m., the scene was quiet except for investigators and a few media representatives.

CTA Blue Line buses waited at the entrance to shuttle passengers to and from the Austin Blue Line stop, stopping in Harlem and Oak Park while the train sat on the platform.

Anyone with information about the shooting is asked to contact the Forest Park Police Criminal Investigation Division at (708) 366-2425 or [email protected].

This is a developing story. Check back for updates.

Collaboration: Cindy Hernandez and Kyra Senese